Do foot orthoses exert there effects via altering sensory input signal?
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Sorry about the table, but I just can't seem to get it formated right.
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I should add a tribute to those brave students who trusted me when I said standing on a block of ice and immersed in ice water would not hurt ..... much ;)
We only had 2 adverse reactions :rolleyes:Last edited by a moderator: Feb 28, 2005 -
Sensory effects of Foot orthotics
Craig;
Nice job as always. I would like to ask a question re: sensory vs. proprioceptive effects. I would assume that they are related, and not mutually exclusive. Though the sensory patterns may be decreased, as in you study, what effect, if any, do you think this had directly on the proprioceptive / positional sense of the patients feet/ limbs?
I would imagine that this would be the next query for you to tackle, if past studies are any indication. Always best to do what you can to seperate out the fact from fiction! ;-)
Keep up the good work!
Sincerely;
Bruce Williams -
Guest
Do foot orthoses exert their effects via altering sensory input signal?
Craig,
Having used the ice immersion technique previously (see paper in Gait & Posture), I'd be interested to see how different the first few steps were to subsequent steps, as we found 'thawing out' to be a major issue. In our study, we were only able to collect three two-step gait initiation trials before the effect appeared to be wearing off. In addition, we also observed (but did not measure) an increase in base and angle of gait when the feet were numb, which might have created some difficulties visualising the frontal plane measurements.
My guess on this one is that tactile sensory input probably is important in relation to balance, gait and postural control (as well as response to foot orthoses), but only in those with some degree of sensory deficit. There's some good emerging evidence that you can augment plantar tactile input to produce beneficial changes in postural control, particularly in older people (see paper by Brian Maki).
Cheers,
Hylton -
<added> I notice in your paper that you iced both feet for 30mins - we only did the one foot for 10mins (we weren't as mean as you :p) - your subjects probably had a much higher level of 'anaethesia' - we just wanted a reduced level of sensory input... - this may account for the wider base of gait differences </added>Last edited by a moderator: Feb 28, 2005 -
Bruce asked:
There is no doubt about the need for and contribution of plantar sensory input to balance - we were just testing if orthoses still had the same mechanical effect if you altered sensory input levels (they didn't) -- foot orthoses do improve balance, but not sure what that has to do with reducing patient's symptoms.
I like to consider plantar sensory input to be a very different beast to proprioception (which is all about joint position sense) ... I know many make claims that foot orthoses may work via proprioception (I wonder if they know what the word means :rolleyes: ), but I need to be convinced how they would do that :confused: How does changing a joint's position with foot orthoses, improve or change the proprioceptive signal from that joint :confused: - to me the signal will be the same, except the joint will be in a different position - how will that lead to an improvement in symptoms :confused: Foot orthoses may provide more signals that the CNS can combine with proprioceptive signals and other inputs ---- this may be how foot orthoses improve balance ---- but as we showed above there are no differences in the mechanical function of the device, that affect the patients symptoms. How would an improvement in proprioception improve patient symptoms (unless they are balance related :confused: )
I was a huge fan of the potential of these possible sensory or neuromechanical functions of foot orthoses. The above is the 3rd study we have done and no effects have been found (the first used Pedar and subjects function measured with and without foot orthoses before and after post tib nerve blocks --> no differences; the second was an RCT using rigid insoles vs soft insoles in soft shoes (aka Robbins & Gouw et al stuff) -- no differences in function at 4 weeks). -
Thanks for the response. Re: your "patients" for these trials/studies. I think yoiu said they were students. Perhaps they are so young and good at compensation, and have few if any mechanical problems in the feet etc., that they don't or won't show too many changes. I don't really know.
I'm not challenging your studies or results by any means! Just thinking out loud.
Re: improvements in balance related to mechanical function. I do have experience in that realm, though not in a study related format as do you. Most of my patients have sever assymetries before hand in their foot function and need for compensations to correct/per se for these balance issues. I've never thought to ask any of them to come back for a PT block to see if they continue to function so well w/ their devices after they've aclimated. Maybe some day.
Re: proprioception, as you say, " Foot orthoses may provide more signals that the CNS can combine with proprioceptive signals and other inputs ---- this may be how foot orthoses improve balance ". I think Howard Dananberg has commented that the CNS or a certain pathway can only carry one type of signal at a time, i.e proprioceptive, or pain. Not fully crediting Eric Fuller here, but Eric's contention is that if there is positional pain, I like to refer to it as interference of sagittal plane motion, that the foot will react to this. IN other words, if there is no restriction in forward motion or mechanical delay in the process, then the proprioceptive signal is not interrupted by a painful signal that something mechanical is wrong. This, I assume would directly aid in balance. My opinion only.
Thanks Craig. Keep up the good work and say hello to your lovely wife for me!
Sincerely;
Bruce Williams -
At the end of the day, the question was "Do you have to feel a foot orthoses to respond mechanically to it?" and the answer was no.Last edited: Mar 1, 2005 -
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Guest
I think they need to look up a dictionary as to what propioception is before they make the claims that they do. What they are doing is NOT proprioceptive - its is something else (probably stimulus of some primitive reflexes).Why? We just showed that the mechanical effect of foot orthoses (ie those related to symptoms) are NOT mediated by sensory input.What they are doing in CP and similar conditions has been well documented in the literature and is widely used in clinical practice and is NOT related to the mechanical effects we see with the functional foot orthoses used for biomechanical symptoms.
Guest
Craig said:
I don't think you can write off the whole concept just yet, Craig, as the study was fairly small (n=13), and, in the words of Altman and Bland, "absence of evidence is not evidence of absence" (see BMJ paper). That is, it is still possible that there is an effect but you didn't find it as the study may have been underpowered.
Having said that, I agree with your concerns that we may be jumping on the neurophysiological bandwagon in relation to foot orthoses a little too quickly. There's still a long, long way to go before we understand how tactile mechanoreceptors contribute to gait patterns, let alone how their function can be modified in a targeted manner with foot orthoses.
Cheers,
Hylton
Guest
Arztin:
Since shin splints can include many different diagnoses, I would think it would be difficult to understand how a crest pad worked for "shin splints" since we don't know if "shin splints" means anterior compartment or posterior-medial compartment muscle strain, chronic exertional compartment syndrome, medial tibial stress syndrome, peroneal muscle strain or tibial or fibular stress fracture. In addition, just because a crest pad worked, there may be many reasons why it worked. I don't understand how a crest pad could "stimulate the receptors of the flexor tendons in the plantar sulci of the toes to relax so that the extensor tendons do not have to work as hard"?? Do we really know that the flexor tendons in the digits have sensory organs within them? Do we also know that these supposed sensory organs within the flexor tendon with the plantar sulcus area of the digits connect via afferent pathways to a reflex arc that sends efferent neural signals to the anterior muscle group, or is this just speculation??
Thats NOT proprioception!! - all the texts I have on my desk define proprioception as something like "the ability to sense ones own body position" - what you are talking about a possible different neurophysiological response.
BTW - the mechanism you are talking about is flawed. How does stimulatng the "receptors of the flexor tendons in the plantar sulci of the toes to relax so that the extensor tendons do not have to work as hard" actually work? - the muscles are not even working at the same time during the gait cycle!